The practice of joint replacement surgery is now several decades old. The steps for this surgery involve exposing the cancellous bone, and in many locations, the intramedullary canal
A properly shaped cavity must be created in the bone to accept the insertion of the prosthetic implant and any bone cement which may be inserted to secure the prosthetic implant in position.
In cases where an intramedullary canal is involved, a plug of bone, bone cement or plastic, a "intramedullary plug", is inserted into the intramedullary canal at the lowest level for the bone cement to fill and reach. Thereafter when the bone cement is inserted under pressure, and even more so when the prosthetic implant is inserted, the bone cement is forced into the intertrabecular spaces of the cancellous bone. This achieves mechanical interdigitation of cement and bone, thus maintaining the prosthetic implant in position and preventing it from becoming loose.
The air, blood, fluids, fat, marrow, tissue and bone debris in the intramedullary canal and the intertrabecular spaces of the adjacent cancellous bone must be removed from that area before the bone cement will be able to penetrate to the necessary depth, so that the bone cement is in direct contact with the bone without any interposed material.
The standard method of bone preparation today is surgical lavage, using an irrigating fluid such as sterile saline, followed by suction, to remove the air, blood, fluids, fat, marrow, tissue and bone debris, and then inserting gauze surgical sponge. This accomplishes only incomplete drying of the bone, and only incomplete removal of the air, blood, fluids, fat, marrow, tissue and bone debris, particularly in the small intertrabecular spaces of the cancellous bone in the femur adjacent the intramedullary canal. As a result the penetration depth of the bone cement is less than optimal, and the direct apposition of bone cement to bone is less than optimal, which results in a weaker, less secure fixation of bone cement in the bone. In addition the gauze surgical sponge may leave some cotton fibers in the opening, on the rough sharp edges of the bone, which can lead to osteolysis after the surgical procedure.
The amount of air, blood, fluids, fat, marrow, tissue and bone debris left in the cavity is decreased by inserting the bone cement through a cement gun which introduces the bone cement at the bottom of the cavity. The bone cement thus forces some of the air, blood, fluids, fat, marrow, tissue and bone debris up and out of the cavity as the bone cement is inserted, but also any of those materials remaining in the cavity or the bone may be forced back into the vascular channels as emboli.
The principal adverse complications of joint replacement surgery, listed below, may all be caused by the presence of unremoved significant amounts of one or more of air, blood, fluids, fat, marrow, tissue and bone debris.
Loosening of Bone Cement or Prosthetic Implant. This may occur if the bone surface, the underlying cancellous bone, or the intramedullary canal are not cleaned, dried, and emptied of air, blood, fluids, fat, marrow, tissue and bone debris. These materials may prevent the bone cement from penetrating and filling certain areas and fixation is not as secure as optimal. When fixation is not secure, micromotion may occur and gradually increase, resulting in more serious loosening and eventual failure of the operation.
Air Emboli (air forced into the blood stream). This may occur when room air is left in the intramedullary canal or in the intertrabecular spaces of the cancellous bone prior to the time the bone cement is forced into the intramedullary canal or cancellous bone. This air may be forced into the circulatory system when the bone cement and then the prosthetic implant is forced into the bone. While it is rare for large emboli to form, that is a very serious complication.
Embolization of other substances in the intramedullary canal such as blood, fluids, fat, marrow, tissue and bone debris. This occurs in a similar manner as air embolization, as described above. This also may be a very serious complication.
Contamination of the operating room and personnel with the patient's air, blood, fluids, fat, marrow, tissue and bone debris occur when the materials are blown out of the cavity and are not directed, confined and collected.
Nearly sixty years ago, a combination compressed air and suction instrument was disclosed for use in oral surgery, U.S. Pat. No. 1,987,907, granted Jan. 15, 1935, Combination Surgical Air Blast and Suction Tip, Joseph B. Jenkins. The use of carbon dioxide, as the compressed gas, in these instruments was disclosed in U.S. Pat. No. 2,812,765, granted Nov. 12, 1957, Combination Aspirator and Fluid-Delivering Surgical Instrument, Benjamin F. Tofflemire. The use of compressed air to dry a bone prior to attaching a dental implant is disclosed in U.S. Pat. No. 4,380,435, granted Apr. 19, 1983, Permanent One Visit Bonded Bridge No Drilling, and Kit Therefore, Arthur Raeder; Celia R. Raeder.
The use of carbon dioxide in joint replacement surgery to flush air out of the intramedullary canal and adjacent cancellous bone just prior to the insertion of bone cement was shown to eliminate clinically detectable air emboli in Prevention of Air Emboli in Hip Surgery, Harvey, PB and Smith, JA, Anesthesia, 1982, Vol. 37, pages 714-717. To prevent loosening of the prosthetic implant from occurring, all available methods should be used to clear the intertrabecular spaces of all air, blood, fluids, fat, marrow, tissue and bone debris, to a depth of 6mm prior to introduction of the bone cement, Noble, P. C. & Swarts, E., Penetration of Acrylic Bone Cements into Cancellous Bone, Acta. Orthop. Scand. 54, 566-573, 1983.
U.S. Pat. No. 5,037,437, granted Aug. 6, 1991, filed Jan. 19, 1990, titled Method of Bone Preparation for Prosthetic Fixation, Frederick A. Matsen III, also discloses the use of carbon dioxide to "blow out" the air, blood, fluids, fat, marrow, tissue and bone debris from the intramedullary canal and to dry the cancellous bone. The configuration of the delivery nozzle is not disclosed and is stated to be not critical. Concurrently with the application of the carbon dioxide, suction to the bone may be employed to remove the debris and liquids dislodged by the compressed gas.